Jet nozzles of the type to which the present invention is directed are well known in the art. They are used in association with coating lines for applying a coating to a continuous web or strip of substrate such as cloth, paper, film, foil or metallic strip. The substrate continuous web or strip is coated with the desired coating material by any appropriate means such as means for spraying the coating material on the web or means for causing the web to pass through a bath of the coating material. While the coating material is still in a liquid state on the substrate web, the web is caused to pass by or between one or more jet nozzles. The jet nozzles comprise elongated members located close to the web surface or surfaces and extending transversely thereof. The jet nozzles each have an elongated discharge gap, also extending transversely of the web, through which a fluid medium (generally a gaseous medium) is cause to impinge upon the web surface or surfaces. In this way, the jet nozzle or nozzles are used to remove excess coating material and to render the coating more uniform throughout the width of the web or strip. Jet nozzles, in some coating operations, have also been used as back-up or support means for the web.
While not intended to be so limited, for purposes of an exemplary showing, the present invention will be described in its application to jet nozzles used in association with metallic coating lines for applying a molten coating metal to the surface or surfaces of a base metal strip. For example, it is common practice to utilize jet nozzles as finishing means in coating lines for coating a ferrous base metal strip with a molten coating metal such as zinc, zinc alloys, aluminum, aluminum alloys, terne and lead.
When the coating operation is a conventional hot-dip operation, jet knives are located to either side of the strip as it exits the bath of molten coating metal. The jet knives are located quite close to the strip surfaces and direct a finishing medium against the strip surfaces. The finishing medium may be air, steam, nitrogen or an inert gas.
In the typical coating operation, coating splashback can occur with the result that there can be coating metal build-up within the jet nozzle discharge gap. It is not uncommon to locate the jet nozzles directly opposite each other on either side of the coated strip. Under these circumstances, additional coating metal can be blown by one jet nozzle into the other. If the build-up of coating material within the jet nozzle gap, or on the lips of the jet nozzles which define the gap, becomes excessive, uniform coating weight control is impaired; coating streaks can occur; and the built-up coating metal can even scratch the surfaces of the coated strip.
Foreign particles originating from the internal chamber of the jet nozzle can also become lodged in the gap. The particles are forced into the gap by the finishing medium. If not removed, they can cause non-uniform coatings or coating streaks.
Removal of coating metal build-up on the jet nozzle lips or in the jet nozzle discharge gap is frequently difficult because of the inaccessibility of the jet nozzles. This is particularly true where the finishing step is performed in an enclosed atmosphere, such as is taught in the one-side coating procedures set forth in U.S. Pat. Nos. 4,082,868; 4,114,563 and 4,152,471. U.S. Pat. No. 4,330,574 teaches enclosed finishing utilizing jet nozzles within an enclosure.
The necessity for cleaning the jet nozzles and the problems attendant therewith have long been recognized by the worker in the art. In many instances it has simply been necessary to shut down the line, and remove the jet nozzles for cleaning purposes. Jet nozzles have been made of a clam shell construction to facilitate the cleaning thereof. Such jet nozzles are taught, for example, in U.S. Pat. No. 3,314,165.
Another approach by prior art workers has been to use a wire brush or a small diameter wire mounted on the end of a long handle means. The brush is forced against the nozzle gap and moved therealong, or the wire (bent at right angles) is positioned within the gap and moved the length of the nozzle. Both of these methods are difficult to perform, particularly when the nozzle gap is in close proximity to the strip. Furthermore, both methods require that the operator be subjected to heat and hot nitrogen or air blasts.
Other methods have been devised both for cleaning air nozzles and for preventing the build-up of coating material on the lips or within the discharge gap of the air nozzles. For example, jet nozzles have been provided with a rod located internally of the jet nozzle, with one end of the rod extending through the end plate of the nozzle body. Within the nozzle, a thin metal blade is mounted on the rod. The thin metal blade extends through the nozzle gap and the rod is shifted manually to cause the blade to traverse the length of the nozzle gap for cleaning purposes. U.S. Pat. No. 2,135,406 teaches a jet nozzle provided with means whereby a portion of the finishing medium within the nozzle and under pressure is channeled to a distribution chamber located on the bottom exterior surface of the nozzle. From the distributing chamber, the air exits through a narrow slot or opening which directs the air under pressure onto the bottom surface of the nozzle and directly across that portion of the nozzle where coating material often tends to accumulate. U.S. Pat. No. 2,679,231 utilizes secondary air and a specially configured baffle means to avoid build-up of the coating material.
The present invention provides a cleaning means which can be mounted adjacent to or directly on the jet cleaning nozzle. The mounting is such that the cleaning device, having a blade extending into the discharge gap of the nozzle, can be readily made to traverse the length of the nozzle (with the blade cleaning the gap) by means of an elongated pole, or preferably by motorized operation which requires no access to the jet nozzle by the operator and eliminates subjecting of the operator to jet blast, heat and the like.